Method

Preheat the oven to 200C/400F/gas 6. Peel the onions, finely slice into rounds and place in a bowl. Add the balsamic and a couple of good pinches of sea salt to draw out excess moisture (you’ll drain the liquor off, so don’t worry about the amount of salt).

Put the minced beef into a bowl with a big pinch of black pepper and a small pinch of salt. Drain and add the beans. Separate the egg and add the yolk to the mixture, then scrunch together really well with clean hands. Whisk the egg white, halve your burger buns, put back together, brush just the tops with egg white, then scatter over the sesame seeds to create a nice, even layer (you can even make stencils for a bit of fun, if you want to get the kids involved).

Pull off any tatty outer leaves from the cabbage. Very finely slice it, ideally on a mandolin (use the guard!). In a large bowl, toss the cabbage with the yoghurt, mustard, chilli flakes, lemon juice and a pinch of black pepper.

Divide the burger mixture into six equal-sized balls. Place two large non-stick ovenproof frying pans on a medium-high heat with 1 teaspoon of oil in each (or cook in batches). Add three balls of mixture to each pan, gently squash into patties about 2cm thick, cook for 2 minutes, or until golden, then flip over. Top each burger with a slice of mozzarella and strip in the rosemary leaves around them. Pop into the oven for 2 minutes so the mozzarella melts, with the buns alongside to warm through. Slice the tomatoes and divide between the bun bases with the cheesy burgers, crispy rosemary and balsamic onions, then pop the tops on, toss the slaw with the rocket, and serve.